The present invention relates to a testing apparatus, and a testing method, for pressure testing bottle closures. Particularly, the invention relates to an apparatus which utilizes a testing vessel having a bottle finish for receiving a bottle closure thereon, and having a pressurizing source and a monitoring device for determining the pressure retaining capability of the closure.
Plastic closures are known for closing and sealing plastic bottles. Particularly, such closures are used for plastic bottles holding pressurized carbonated beverages. Such closures are described, for example, in U.S. Pat. Nos. 5,800,764 and 4,497,765.
In order to maintain the desired pressure within a carbonated beverage bottle, the associated bottle closure must seal to the bottle finish effectively, maintaining a seal even under adverse conditions. Such adverse conditions can include temperature variations, humidity variations, and external physical or mechanical forces.
To ensure quality control of manufactured bottle closures, an industry standard method of testing the pressure retaining capabilities of closures has been developed. An industry accepted method involves the pressure testing of a sample bottle that is fit with the closure to be tested. The bottle is pressurized with a pressurizing media, such as carbonated water, and a pressure reading is taken after a preselected time. The bottle is pierced with a gauge, such as with a Zahm Nagel gauge, and the pressure in the bottle is instantaneously measured.
While this method measures the pressure maintained by the closure, the method also destroys the bottle such that the test bottle and associated closure cannot be used for a subsequent pressure measurement. Accordingly, the sample size of the test is necessarily increased. The number of pressurized bottles that must be prepared is increased. The statistical accuracy of the test is limited.
As a further drawback to this test, measuring the pressure within the test bottle includes other variables such as gas permeation through the bottle, and bottle expansion under pressure that reduce the accuracy of the pressure measurement.
Another apparatus that has been used to test closures includes a bottle neck including the bottle finish, cut from a bottle and mounted on a metallic fixture. The fixture is pressurized with air and instrumented. The fixture, including the bottle finish, and the closure cap, is submerged in a water filled tank. Any escaping air from the pressurized fixture can be observed as air bubbles. This test apparatus has an advantage in measuring accuracy over the previously described apparatus in that the variables of bottle expansion and gas permeation are eliminated. However, because the bottle finish is distorted during the pressure test, the procedure requires the preparation of cut-off bottle necks for each test. The base of each bottle neck must be cut and then polished, which are labor intensive additional steps procedures.
The present inventors have recognized that it would be desirable to provide a bottle closure testing apparatus and method which overcomes the drawbacks of the prior apparatus and methods. The present inventors have recognized that it would be desirable to provide an apparatus which is easily configured for receiving closures to be tested, and which could be sufficiently portable to be used to test closures in different environments. The present inventors have recognized that it would be desirable to provide an apparatus which provides accurate test results and which can be used for testing a closure more than once and for a prolonged duration.
The present invention contemplates a testing apparatus for a closure which incorporates a pressurized, substantially cylindrical, plastic testing vessel as part of the apparatus, for receiving a closure to be tested. The plastic testing vessel can effectively be a disposable component for testing closures. The plastic testing vessel is a relatively thick-walled, tubular vessel having a bottle finish at a top end thereof and a closed bottom end. The plastic testing vessel advantageously comprises a readily available plastic bottle xe2x80x9cpreformxe2x80x9d that exists as an intermediate stage in the blow molding of a plastic bottle.
The testing apparatus provides a base block having a pressurized media input port and a vessel holder. The vessel holder is configured to hold one of the plastic testing vessels therein. The plastic testing vessel includes a pressure entry port in sealed fluid communication with the pressurized media input port. Thus, a closure can be tightened onto the bottle finish of the plastic testing vessel and pressure tested via the pressurized media input port and the pressure entry port.
The base block can include a signal port for monitoring the pressure maintained by the plastic testing vessel and associated closure. The signal port can be monitored by a pressure gauge, or by a centralized system that includes a pressure transducer at the base block that is signal-connected to a data display and/or recorder, such as to a computer via an A/D converter.
Preferably, the base block is part of a separate test module that is mounted to an elongated base plate. Further identical test modules can also be mounted to the base plate, and thereby define a multiple closure testing apparatus. Each of the modules includes a base block having a vessel holder, and a pressurized media input port associated with the vessel holder. A plastic testing vessel having a pressure entry port is held by each of the vessel holders. Accordingly, a plurality of closures can be tested simultaneously on the base plate.
The base plate can be relatively portable to transport the closures being tested into a variety of environments, such as a cold test room, a hot test room, or a humid test room, to test the durability of the closures. The modules are configured such that the closure being tested has an overhead clearance for allowing mechanical loading of the closure for further tests.
Preferably, the vessel holder includes a slot which receives one half of the plastic testing vessel, and a clamp block which clamps the testing vessel into the slot. A nozzle member protrudes into the slot toward the clamp block, and penetrates the pressure entry port of the plastic testing vessel as the plastic testing vessel is driven into the slot by the clamp block. The nozzle member is in fluid communication with the pressure input port. An O-ring seal acts to seal around the nozzle member, and to seal around a sidewall of the plastic testing vessel.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.